There are known devices for dewatering sludge of the general type above referred to in which cakes formed of sludge to be processed are guided between two filter bands about the circumferential wall of a drum. As a result, a certain percentage of the water contained in the cakes is removed as the cakes are guided about the drum.
A method using this mode of dewatering sludge and also a device for carrying out the method is described, for instance, in German DTAS No. 1,960,787. This patent describes a dewatering press in which filter bands are guided partly about the circumference of a single drum, the sludge to be processed being carried between two filter bands. It has been found that such an arrangement does not result in an economically acceptable dewatering efficiency.
There are also known devices for the purpose from U.S. Pat. No. 2,111,720 and German Pat. No. 689,090, in which guidance of filter bands used for causing dewatering of the sludge is similarly unfavorable with respect to efficiency.
Tests have shown that the shortcomings of dewatering devices as previously described are caused primarily by an insufficient break-up of the sludge during the dewatering operation itself.